Gliederung

High expression levels of the S100A4/metastasin gene are associated with cancer metastasis. Here we demonstrate that S100A4/metastasin expression is directly controlled by beta-catenin/TCF signalling in colon cancer cell lines. We used cell lines heterozygous for gain-of-function and wild-type beta-catenin, and knock-out variants thereof homozygous for gain- or loss-of-function mutations in beta-catenin, which were generated by homologous recombination. Based on cDNA array results, genes were identified whose expression is dependent on the beta-catenin genotype. Cell lines that carry gain-of-function beta-catenin mutations expressed high levels of S100A4/metastasin. In parallel, cell migration and invasion of these cell lines were also strongly increased. Transfection of S100A4/metastasin cDNA also increased the migratory phenotype. In contrast, knock-down of S100A4/metastasin by siRNA treatment blocked these biological effects. More importantly, beta-catenin-induced cell migration was also knocked down following S100A4/metastasin siRNA transfection. Furthermore, we have shown that the S100A4/metastasin gene promoter contains a TCF-binding site, which mediates direct binding of heterodimeric beta-catenin/TCF complexes and induces transcriptional activity. Finally, S100A4/metastasin was found to be increased in metachronously metastasizing primary colon cancers, in comparison to non-metastasizing primary tumors. Patients with primary tumors expressing low S100A4/metastasin had longer overall survival and longer metastasis-free survival than patients with high S100A4/metastasin levels. Our data demonstrate that S100A4/metastasin is a direct beta-catenin/TCF target, which induces cell migration and invasion in cell culture, and has potential value as a predictor of metastasis formation in colon cancer patients. These results demonstrate the interconnection of two previously unrelated cellular programs which have been shown to be important for tumor progression and metastasis: the Wnt/beta-catenin signalling pathway and the biological effects caused by the metastasis-associated gene S100A4/metastasin. Our findings that beta-catenin controls S100A4/metastasin directly, and that beta-catenin-induced effects on cell migration and invasion are mediated by S100A4/metastasin, highlight the importance of this pathway for colon cancer metastasis. The data also suggest that S100A4/metastasin is an important target for therapeutic interventions.